What's The Difference Between SPF 30 and 50?
Dr. Elaine Kung, dermatologist and founder of Future Bright Dermatology, explains: "SPF 30 sunscreen only allows 1/30 of the sun's UVB rays to penetrate your skin. That means it blocks about 96.7% of those harmful UVB rays. SPF 50 sunscreen only allows 1/50 of the sun's UVB rays, blocking 98% of them. So, SPF 50 is more protective than SPF 30, but only by about 1%."
Caroline Schmidt in Science